Electroencephalographic Changes During and After Treatment of Hyperthyroidism

Abstract

EEG and thyroid function tests have been studied in 32 hyperthyroid patients before, during and after antithyroid treatment. EEG abnormalities such as increase in alpha rhythm, slow rhythms, spikes and sharp waves and fast activity were found in 81% of the patients before treatment. A statistically significant correlation was found between the degree of EEG abnormalities and the severity of hyperthyroidism. During treatment and the period of observation which was extended to an average of 2½ year, a slight decrease in the occurrence of all abnormalities was observed, but even in the period 24–36 months after the start of the therapy, 65% of the patients still had abnormal EEG's. These persistent abnormalities in EEG suggest that hyperthyroidism might cause irreversible damage to the brain cells. It should be realized that hyperthyroidism may be the cause of considerable EEG abnormalities however not only in the acute state of the disease but also several years after an otherwise successful antithyroid treatment.

EEG Changes in Untreated Hyperthyroidism and under the Conditions of Thyreostatic Treatment

“…We found further a significant higher dominant EEG frequency in hyperthyroid patients, but no exact correlation to T3-values or differences between the two patient-subgroups. This is in accordance with the results by Zander Olsen et al (1972).…”

“…Especially the reduction of abnormal slow-wave activity was only tendiative. This is in agreement with other observations, that EEG disturbances and behavioral abnormalities in previously hyperthyroid patients occurred after treatment permanently over years (Zander Olsen et al, 1972;Junker et al, 1976;Perrild et al 1986). It must be considered, that some of the observed EEG abnormalities, such as disturbances in the slow frequency band of EEG, arc not pathognomonic for hyperthyroidism, they also could be caused by different severe metabolic diseases with cerebral involvement.…”

“…The observed relation between EEG disturbances and the intensity of hyperthyroidism, especially the increasing occurrence of abnormal fast-and slow-wave activity with paroxysmal features and the abnormal photic reactivity in patients with higher pretreatment T3-level, is in agreement with earlier reports Zander Olsen et al, 1972). We found further a significant higher dominant EEG frequency in hyperthyroid patients, but no exact correlation to T3-values or differences between the two patient-subgroups.…”

“…Different correlations between EEG disturbances and the intensity of hyperthyroidism were found. EEG studies including a post-treatment investigation report about incomplete restitutions of cerebral and behavioral dysfunctions in therapy induced euthyroid status and a re-increase of abnormalities in relapses (Howard et al, 1964;Whybrow et al, 1969;Zander Olsen et al, 1972;Spatz et al, 1975;Perrild et al, 1986).…”